Thank you for posting this, I came here to say pretty much the same thing.
The only thing is that I don't agree that post-modernism is totally to blame for nihilism. I think as our access to information about the world increases, we are naturally going to see that reality is subjective. Post-modernism is the only philosophy that has really tried to deeply tackle that, albeit in a very flawed way. You can study 100 cultures and their thousands of different values and beliefs. Add a lot of privilege to that, like a society with a relatively high standard of living, and people just don't know what to do with themselves. They don't know how to choose because everything seems like a subjectivity trap. This is not trivial, it is crushing. I know people who are in their 40's who have been paralyzed by this for more than a decade. They realize that nothing has inherent meaning, so what's the point of doing anything? How do you choose?
Traditional culture, even though it's very limited, made the choice for people... and there was no knowledge base with which to counter it. It left a lot of people hanging high and dry who couldn't conform, but on the whole you knew your role at birth. Post-modernism has obliterated that. It literally won't allow any structure, and yet that is, in of itself, a structure... one which is being forced on everybody. A structure rooted in high-faluten academia that is now being tested upon the population, just like how French Marxism got tested on the Cambodian people by Polpot.
Hedonism and selfishness are natural products of godlessness. If you can't or won't hand over these difficult questions to a higher power, then you will find yourself at other more tenuous altars of worship: human culture, addictions (from minor ones to really problematic ones), lovers, career, nationalism, fantasy worlds (books, movies, etc.)... anything to ease the pain.
I don't think going back to traditional culture is necessarily the answer. Post-modernism is right that there are an infinite number of ways of viewing the world. The thing is, we're still biological beings and that's going to determine a lot of our meaning automatically. Pretending that isn't real is a form of self-denial. On the other hand, humans have entered a time when we have to create our own meaning, which is difficult if subjectivity has paralyzed you. But you have to do it. And I believe that meaning comes from a spiritual core. There IS something about you that is pre-determined. It's not ALL subjective. In those pre-determinations, you can find what feels right (not just what "feels good"), what resonates, what rings true. Then live by that.
The problem is that post-modernism wants to erase people it doesn't agree with, so we are really dealing with neo-Marxist garbage in our society now, foisted by the rotten intellectuals.